A rotorcraft has at least one turboshaft engine that acts via a main transmission gearbox to transmit power to a rotor for providing lift and possibly also propulsion. The main gearbox and the engine are housed respectively in first and second compartments, and a firewall is generally arranged in the structure of the rotorcraft to separate the first and second compartments. Thus, if the engine accidentally catches fire the second compartment, the fire will not normally propagate into the first compartment containing the main gearbox.
In the known prior art, a firewall is constituted by a metal wall made of steel or titanium, for example, in order to prevent fire propagating.
In normal operation, the cold surface of the firewall facing the main gearbox reaches temperatures either of about 180° C. maximum when the gas exhaust nozzle of the engine is remote from the main gearbox, or else lying in the range 300° C. to 400° C. when the gas exhaust nozzle of the engine lies beside the main gearbox.
The rotorcraft certification standards that are applicable in particular to the mechanical compartment containing the main gearbox being particularly severe, the risk of fire in that mechanical compartment must be minimized to the greatest possible extent.